In conventional band stop filters for high frequencies, a plurality of series resonating circuits are connected via transmission lines, and when the center frequency is below 1,000 MHz, coaxial cables are used as the transmission lines so as to make the band stop filter small in size. Each of the coaxial cables used in such a band stop filter has a length which substantially equals one quarter wavelength at the center frequency. Although the conventional band stop filter having the above-mentioned structure has symmetrical frequency characteristic with respect to the center frequency, the sharpness of the frequency characteristic, namely the sharpness of the band rejecting characteristic, is not satisfactory. Furthermore, the insertion loss in the transmission band should be as low as possible. However the insertion loss of the conventional band stop filters is not satisfactorily low for some uses.